What principle does chromatography operate on?

Chromatography operates on the principle of separation based on different affinities of substances to the stationary and mobile phases. In this technique, a mixture is dissolved in a mobile phase (which can be a liquid or gas) and then passed through a stationary phase (which is usually a solid or a liquid supported on a solid). As the mobile phase moves through the stationary phase, different components of the mixture interact with both phases to varying degrees based on their chemical properties, size, polarity, and other factors.

Substances that have a higher affinity for the stationary phase will move more slowly, while those that prefer the mobile phase will move more quickly. This differential migration results in the separation of the components as they travel through the stationary phase. Thus, the final separation achieved in chromatography is fundamentally due to the differing affinities of the substances in the mixture for the two phases. This principle is widely applicable in various fields, including biochemistry, analytical chemistry, and environmental science, for separating and analyzing complex mixtures.